Lightning areestee



P 17, 1929- L. R. GOLLADAY ETAL 1,728,559 I LIGHTNING ARRESTER Filed Feb. 1, 1927 WITNESSES aurence a a a 126 and/7779 5 5/290 A'TTORNEY Patented Sept. 17, 1929 UNITED STATES,

PATENT OFFICE LAWRENCE R. GOLLADAY, OF EAST PITTSBURGH, AND IRVING B. SMITH, OF PITTS- BURGH, PENNSYLVANIA, ASSIGNORS TO \VESTINGHOUSE ELECTRIC AND MANU- FACTURING COMPANY, A CORPORATION OF PENNSYLVANIA LIGHTNING ARRESTER Application filed February 1, 1927.

Our invention relates to electrical protective devices and especially to casings for the same.

One of the objects of our invention is to provide a lightning-arrester easing having the rugged construction required in lightning arresters and yet having means for securing a positive destruction of the arrester due to a failure of the same.

Another ob-jectof our invention is to provide a lightning-arrester casing which will visibly indicate a failure of the same. In the accompanying drawing, the single figure is a View, partially in elevation and partially in cross-section, of a preferred embodiment of our invention.

A substantially cylindrical casing member 1 is provided with an axially disposed cylindrical chamber 2. The casing member 1 is similar to a distributiontype insulator and has projecting flanges or skirts 3.

Disposed in the chamber 2 is a (Lischarging means 4 comprising a stack of resistance disks or plates separated by mica spacers or washers. The discharging means is similar to that described in Slepian Patent No. 1,509,493, issued September 23, 1924.

Secured to the end face 5 of the casing member is a separate circular cup-shaped porcelain member 6 which retains the disks 4 in the chamber 2. The cup-shaped memher 6 has an annular rim 7 which is glazed to the end surface 5 of the casing member 1, securing the cup-shaped member (3 there to. Disposed adjacent to the annular rim 7 is a side-wall portion 8 of reduced thickness. The bottom 9 of the cup-shaped member 6 is provided with a perforation 10.

When abnormal heating occurs in the arrester, as a result of a failure thereof, which would permit the line current to follow a discharge therethrough, the portion 8 of reduced thickness will be subjected to a lateral stress, due to the expansion of the bottom disks 4 or the bottom terminal plate 11 of the discharging means thereby causing the cup-shaped member 6 to be severed at the said portion 8 of reduced thickness.

A flexible ground-lead 12 projects through the perforation 10 in the cup-shaped member Serial No. 165.104.

(3, and one end of said ground lead is soldered to the metallic disk or terminal plate 11 upon which the stack of discharge elements 1 is supported.

Vv'hen a failure of the arrester occurs, the

cup-shaped member 6 will be fractured, as set forth above, and will permit both the stack of disks 4 and the flexible ground lead 12 to-fall free of the casing member.

The inner diameter of the rim or upper portion of the cup-shaped member 6 is made slightly greater than the diameter of the chamber 2- in order that no restriction may be imposed upon the freedom with which the disks fall free of the casing member.

The lower end of the casing member 1 is extended to form a tubular projecting portion 13 which provides a protection for the cup-shaped member 6. Thisis necessary since, although the cup-shaped member 6 is relatively strong against axially applied stresses it is inherently weak as to radially applied stresses.

\Vhen it was first attempted to make a frangible drop-out bottom for lightning arresters the casing was made in one piece of dry-process'molded porcelain. This process consists in compressing a quantity of relatively dry ingredients between two faces of a die or mold, thereby forming the member which is subsequently fired. hen the upper portion of the die was withdrawn, the thin wall portion was forced out by the suction created in removing this portion of the die, thereby causing an enormous loss in the process of manufacture. Furthermore, it was not easy, with the old process, to obtain exactly the dimensions desired, and it was practically impossible to inspect or gauge the finished casing to check the thickness of the thin-wall portion, owing-to the fact that there was no room, in the finished product, to apply calipers or other gauging means to the thin-Wall portion.

An attempt was made then to manufacture such a casing by the pugging process, which consists in forming the piece in approximately thedesired shape and subsequently turning it to the exact dimensions re quired. It is very difficult to turn, on a lathe.

a piece having such shape as is shown in the accompanying drawing. In addition, it was substantially impossible to gauge the thickness of the thin-wall portion, as has already been mentioned. v

The proper operation ofthe drop-out bottom is dependent upon the thickness of the section which is fractured by the occurrence of abnormal heating in the lightning arrester.v It is necessary to make this reduced section so thin that it will be fractured very quickly after the failure of the arrest-er occurs. However, in order that the thin-wall portion may have suflicient strength to withstand the shocks incident to transportation and installation, it is necessary. that it shall be as thick aspossible without substantially infipairing the heat-responsive qualities there- 0 v By our invention, we provide a separate "member having a thin-wall portion, said member being manufactured by the dry process. Since thismember is made separately from the casing member, the dimensions may be checked very accurately before attaching the same to the m ain body of the casing.

The main body of the casing,.being now of an easily-turned shape, may be 'made by puggingor extruding, which process not only provides a "ery good quality of porcelain, but also is relatively inexpensive.

.The cup-shaped member is secured to the main casing member before either member has been fired, and the parts are glazed together during the firingoperation. The flexible-ground lead and the discharge elements are inserted in the casing through the open top thereof which is subsequently closed by suitable means (not shown)".

It is apparent that our invention is a valuable contribution to the art of making lightning arresters, in that. it provides a means for visibly indicating the failure of an arrester, which is positive and which may be predetermined to a high degree of accuracy.

Although we have described our invention with reference to a specific example of the construction thereof, it is apparent that our invention is not limited to the details shown, and we desire that the appended til) permitting the circular central portion to be severed from the casing member by abnormal heating occurring in the electrical protective device and to fall free thereof.

3. A. protective device comprisingamassive main casingmember ofwet-process porcelain, said casing member having arr axial perforation or chamber, anda down-'- wardly depending protecting skirt extending below the lower end offsaid' -perforationyor chamber, a cup shaped bottomine'mber of dry-process porcelain glazed to said main casing meinber' near the junctionof said downwardly depending'skirt and said lower end of said perforation-Qrchamber, said cup shaped member having thin sidewalls constituting a continuation of said perforation or chamber in said main casing'member, and discharge "elements disposed in said perfora tion or-chamber and supported-by said cupshaped member.

In testimony whereof, we have hereunto subscribed our names-this 26th day'of January, 1927. LAWRENCE R.- GOLLADAXZ.

IRVING R; SMITH. 

